Moira Weigel in The Chronicle of Higher Education [h/t: John Collins]:
Jenkins and Ichikawa took the most common charges they had heard against nonmonogamy, and they refuted them one by one.
Take, for instance, the claim that it’s unhealthy to have multiple sexual partners. Jenkins and Ichikawa pointed out that this was simply untrue. It is perfectly possible to maintain sexual health with multiple partners; indeed, a person who has openly discussed the pros and cons of opening a relationship with a partner is more likely to practice safe sex than is the frustrated partner who resorts to "drunken flings, clandestine affairs, or other ill-considered hookups."
What about the assumption that nonmonogamy is psychologically damaging? "Different people are different," Jenkins and Ichikawa wrote. Many nonmonogamous people report that they come to feel less jealousy over time; conversely, many monogamous people complain of experiencing sexual jealousy. In response to the charge that nonmonogamy is "unnatural," Jenkins and Ichikawa pointed out that virtually no species are sexually monogamous, even if they are socially monogamous or pair-bond for life. ("Not even swans.")
They called their letter "On Being the Only Ones." Soon after they published it, they learned that they weren’t. Strangers, and couples they had known casually for years, started approaching them at conferences, they say, and thanking them for writing the piece. Many said they had quietly lived the same way and felt relieved to be able to speak about it. Emboldened by a new sense that she had an activist mission — that her coming out might help others like her, and that she, as a tenured professor, had the privilege to do so — Jenkins began writing more about nonmonogamy. She wrote about it in The Globe and Mail and Slate. She went on CBC to give radio interviews. But even in contexts in which people were willing to give her an audience, they struggled with her argument that polyamory and promiscuity were not the same thing.